The invention relates to a force limiting device for a belt retractor as well as to a belt retractor comprising a force limiting device. The invention further relates to a method of reversing a force limiting device for a belt retractor.
Belt retractors comprising a force limiting device that in a case of restraint prevents the force acting on a vehicle occupant by a seat belt from excessively increasing are known in different configurations. In general it is desired to adapt the characteristic line of the restraining force to the vehicle occupant (size, weight etc.) and/or to adjust it to the current situation. It is common to first of all provide a high force level in any case. If, however, a lower restraining force is sufficient, for example for a light vehicle occupant, after a defined period of time reversing to a lower force level can be provided to relieve the vehicle occupant corresponding to his/her weight. A belt retractor comprising a force limiting device providing such functionality is shown, for instance, in DE 10 2008 063 639 A1.
Upon reversing to the lower force level, the abrupt drop of force can excite the elastically biased belt system to oscillate which is basically undesired as regards an optimum occupant restraint.